负载双金属纳米催化剂表面组成、结构与性能关系

Surface composition and structure of bimetallic nanoparticles are the main factors that determined their catalytic performance. Moreover, the surface composition of bimetallic catalysts has been found to be significantly different from their bulk counterpart. Determining the surface structure and composition is vital important in understanding the roles that affect catalytic performance. In the present project, various noble metals and transition metals including Pt, Rh, Pd, Ru, Ir, Au, Ag, Fe, Co, Ni, Cu et al. will be deposited onto a refractory metal single crystal surface under ultra-high vacuum (UHV). Which will be used to evaluate their related sensitivities of high-sensitivity low energy ion scattering spectroscopy (HS-LEIS). Bimetal films will be synthesized and characterized using HS-LEIS to obtain phase-diagrams of surface composition as a function of the bulk one. Then model oxide thin films including SiO2, Al2O3, TiO2, MgO et al. will be synthesized on the refractory metal surface using as a support. The surface composition of bimetallic nanoparticles grown on the model oxide surface will be determined by HS-LEIS. The surface ensemble of the bimetals will be determined by in-situ Infrared Reflection Adsorption Spectroscopy (IRAS) using CO as a probe. These supported bimetals then will be tested for CO catalytic oxidation or hydrogenation to understand the bimetallic effects, e.g. ensemble effect or electronic effect, as well as the important parameter that controlled the catalytic activities. Detail correlation between the surface composition and catalytic performance can be established. Furthermore, using these model bimetallic catalysts, by combining with modern surface science techniques, the influences of alloying effects on the kinetics, the mechanism, the nature of adsorbed intermediates and the consequences on activity and selectivity can be better understood.

多相催化剂的性能主要决定于最表面层原子及结构，但催化剂的最表面层（特别是工作状态下）的组成通常与相应的体相组成存在显著差别，其定性/定量分析对明确催化剂的性能并进而研制高性能催化剂是不可或缺的。本项目拟在在超高真空环境下，制备不同金属(Pt, Rh, Pd, Ru, Ir, Au, Ag, Fe, Co, Ni, Cu等)的单组份纳米膜和双组份纳米膜、模型氧化物负载双金属纳米粒子，应用新购置的高灵敏度低能离子散射谱仪测定不同金属的相应灵敏度因子，建立双金属纳米膜、负载双金属纳米粒子的表面组成与体相组成的关系相图。应用原位镜面反射红外光谱结合探针分子技术探明双金属膜和负载双金属纳米粒子的表面微结构。以CO催化氧化或加氢作为探针反应，分别考察这些模型体系的催化性能，建立助催剂、活性组分、结构～催化性能的关系，并进而研究其活性位的本质和反应机理、及影响选择性的关键控制因素。

多相催化剂的性能主要决定于最表面层原子及结构，但催化剂的最表面层（特别是工作状态下）的组成通常与相应的体相组成存在显著差别，其定性/定量分析对明确催化剂的性能并进而研制高性能催化剂是不可或缺的。项目研究开展了Pt, Rh, Pd, Au, Ag, Fe, Co, Ni, Cu, Sn, Bi, Ce, Ti等的单或双组份纳米膜、纳米粒子，应用高灵敏度低能离子散射谱仪测定不同金属的相应灵敏度因子、常规氧化物负载单、双组份催化剂的分散度，建立双金属纳米膜、负载双金属纳米粒子的表面组成与体相组成关系的相图。应用XPS和原位红外光谱结合探针分子技术研究双组份催化剂的表面微结构，探索提高催化剂活性组分分散度、增加活性组分载体的界面面积的催化剂制备包括预处理方法。以CO催化氧化或加氢作为探针反应，分别考察这些体系的催化性能，建立助催剂、活性组分、结构～催化性能的关系，探讨了其活性位的本质和反应机理、及影响选择性的关键控制因素。